A turbomachine is known having at least one first and one second impeller wheel whose back faces confront each other, a rotor shaft carrying two radial impeller wheels, and a bearing system. Adjacent each of the radial-blade impeller wheels is an axial bearing with one respective rotor bearing half and one respective stator bearing half. The rotor bearing halves are each formed on the back face of the respective radial impeller wheel.
In practice, to contain the axial thrust of a rotor of a turbomachine using a magnetic bearing system, axial bearing surfaces are customarily used that are either formed directly on the shaft, or fixed by an additional axial bearing washer to the shaft. Correspondingly, turbomachines having an axial magnetically mounted rotor shaft are known in which the magnetic bearing halves for axial bearing are on an axial bearing washer, or on opposed shaft shoulders shrunk onto the rotor shaft.
EP 2 017 435 A2 describes a design having the features cited above for a turbomachine having as short a rotor as possible, and a rotor mass that is as small as possible. Because the rotor bearing halves are formed on the back faces of the radial impeller wheels, the space taken up by the axial bearing can be reduced significantly, the axial bearing halves being integrated into a housing wall and also integrated into the rear side of the radial impeller wheels, which must also be present independent of the bearing. The number of separate components is thereby reduced. The design known from EP 2 017 435 A2 is substantially symmetrical starting at an electric machine located centrally of the rotor between the two radial impeller wheels. Starting at the electric machine, sequentially in both directions, a radial magnetic bearing, a safety bearing, an opening through the assigned stator bearing half having an interior shaft gasket and finally at the end of the rotor shaft, the corresponding impeller wheel is mounted overhung. Starting at the electric machine, the diameter of the rotor shaft decreases in both directions successively, according to the cited components that are provided along the rotor shaft. During assembly, first the rotor shaft must be inserted through with the electric machine into the housing, the further components and finally the two impeller wheels are then installed on the two shaft ends. To make subsequent maintenance possible, the turbomachine must be accessible on both sides, and both axial impeller wheels must be made removable as well.